Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 72: [MA] Joint Session "Surface Magnetism III" (jointly with O)
O 72.3: Vortrag
Donnerstag, 29. März 2012, 15:45–16:00, BH 243
Ultrafast Magnetization Dynamics of Gadolinium and Terbium Studied by XUV Photoelectron Spectroscopy — •Martin Teichmann1,2, Kristian Döbrich1,2, Björn Frietsch1,2, Cornelius Gahl1,2, Robert Carley1,2, Olaf Schwarzkopf3, Philippe Wernet3, and Martin Weinelt1,2 — 1Max-Born-Institut, Max-Born-Straße 2a, 12489 Berlin — 2Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin — 3Helmholtz-Zentrum für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin
Recent results from IR-pump-XUV-probe angle-resolved photoelectron spectroscopy (ARPES) experiments on the ultrafast demagnetization of thin films of Gd(0001) and Tb(0001) on W(110) will be presented. Following excitation by an intense IR pulse, ARPES with 35 eV photons allows us to directly probe the response of the exchange-split valance band. As a signature of ultrafast demagnetization by the IR pulse, we see a rapid reduction of the exchange-splitting in the valence band of both metals. However, due to its larger spin-lattice coupling, the response of terbium to laser excitation is far stronger than gadolinium. We also observe significant differences between the responses of the minority and majority bands in the first picosecond, both within and between the two metals. This ultrafast response is in contrast to quasi-equilibrium thermal demagnetization, and reveals a spin dependence to the exchange coupling between the valence and 4f states responsible for magnetic ordering. Laser excitation drives the system out of magnetic equilibrium on the picosecond timescale.